The prsent application is a U.S. National Application filed under 35 USC 371 of PCT/FR98/02694 filed Dec. 11, 1998, based upon French application Serial No. 98.00424 filed Jan. 16, 1998.
The present invention relates to new tricyclic compounds.
There are known from the prior art 2,3-dihydrophenalene compounds (J. Chem. Soc. C, 1971, 9, pp1607-1609) which are described as synthesis intermediates, and 1,3,4,5-tetrahydrobenzo[cd]indole compounds (EP 353 557) for use in the preparation of platelet aggregation inhibitors.
Moreover, Application EP 737 670 describes tricyclic amide compounds as melatoninergic receptor ligands.
Numerous studies in the last ten years have demonstrated the key role of melatonin (N-acetyl-5-methoxytryptamine) in many physiopathological phenomena and in the control of the circadian rhythm. Its half-life is quite short, however, owing to the fact that it is rapidly metabolised. Great interest therefore lies in the possibility of providing the clinician with melatonin analogues that are metabolically more stable, have an agonist or antagonist character and may be expected to have a therapeutic effect that is superior to that of the hormone itself.
In addition to their beneficial action on circadian rhythm disorders (J. Neurosurg. 1985, 63, pp 321-341) and sleep disorders (Psychopharmacology, 1990, 100, pp 222-226), ligands of the melatoninergic system have valuable pharmacological properties in respect of the central nervous system, especially anxiolytic and antipsychotic properties (Neuropharmacology of Pineal Secretions, 1990, 8 (3-4), pp 264-272) and analgesic properties (Pharmacopsychiat., 1987, 20, pp 222-223) as well as for the treatment of Parkinson""s disease (J. Neurosurg. 1985, 63, pp 321-341) and Alzheimer""s disease (Brain Research, 1990, 528. pp 170-174). Those compounds have also demonstrated activity in respect of certain cancers (Melatoninxe2x80x94Clinical Perspectives, Oxford University Press, 1988, pp 164-165), ovulation (Science 1987, 227, pp 714-720), diabetes (Clinical Endocrinology, 1986, 24, pp 359-364), and in the treatment of obesity (International Journal of Eating Disorders, 1996, 20 (4), pp 443-446).
Those various effects are exerted via the intermediary of specific melatonin receptors. Molecular biology studies have demonstrated the existence of a number of receptor sub-types that are capable of binding that hormone (Trends Pharmacol. Sci., 1995, 16, p. 50; WO 97.04094). It has been possible for various species, including mammals, for some of those receptors to be located and characterised. In order to be able to understand the physiological functions of those receptors better, it is of great advantage to have available specific ligands. Moreover, such compounds, by interacting selectively with one or other of those receptors, may be excellent medicaments for the clinician in the treatment of pathologies associated with the melatoninergic system, some of which have been mentioned above.
The compounds of the present invention are new and have very strong affinity for melatonin receptors and/or selectivity for one or other of the melatoninergic receptor sub-types.
The present invention relates more especially to compounds of formula (I) 
wherein:
A forms with the group to which it is bonded a tricyclic system selected from A1, A2, A3 and A4: 
R1 represents a hydrogen atom, a halogen atom or a linear or branched (C1-C6)alkyl, linear or branched (C1-C6)alkoxy, hydroxy or oxo group,
R2 and R3, which may be the same or different, represent a halogen atom or an Ra, ORa, CORa, OCORa or COORa group (wherein Ra represents a hydrogen atom, an optionally substituted linear or branched (C1-C6)alkyl group, linear or branched (C1-C6)trihaloalkyl, an optionally substituted linear or branched (C2-C6)alkenyl group, an optionally substituted linear or branched (C2-C6)alkynyl group, an optionally substituted (C3-C8)cycloalkyl group, an optionally substituted (C3-C8)cycloalkyl-(C1-C6)alkyl group in which the alkyl moiety is linear or branched, or an optionally substituted aryl group),
the symbols (R2)m and (R3)mxe2x80x2 denote that the ring in question may be substituted by from 1 to 3 groups (which may be the same or different) belonging to the definitions for R2 and R3,
X, when A represents a tricyclic system A1, A2, A3 or A4, represents a sulphur atom, a (CH2)q group (wherein q is 1 or 2), a xe2x80x94CHxe2x95x90CHxe2x80x94 group, or an NR4 group (wherein R4 represents a hydrogen atom or an optionally substituted linear or branched (C1-C6)alkyl group),
xe2x80x83or X represents an oxygen atom when A represents the tricyclic system A1,
n is an integer such that 0xe2x89xa6nxe2x89xa63
p is an integer such that 1xe2x89xa6pxe2x89xa63 when n is 1, 2 or 3 and the 
xe2x80x83chain is in the b position and A represents either a group A2, A3 or A4 wherein X represents a xe2x80x94CHxe2x95x90CHxe2x80x94 group, or a group A1,
xe2x80x83and such that 0xe2x89xa6pxe2x89xa63 in all other cases,
xe2x80x83it being possible for the 
xe2x80x83chain to be unsubstituted or substituted by one or more groups, which may be the same or different, selected from Ra, ORa, CORa, COORa or halogen atoms,
B represents:
an 
xe2x80x83group wherein Ra is as defined hereinbefore, Z represents an oxygen atom or a sulphur atom, and R5 represents an Ra group or an NR6R7 group wherein R6 and R7, which may be the same or different, represent an Ra group,
or a 
xe2x80x83group wherein Z, R6 and R7 are as defined hereinbefore,
the symbol  denotes that the bond may be single or double provided that the valency of the atoms is respected,
xe2x80x83it being understood that the symbol 
xe2x80x83is used to denote the formula 
xe2x80x83(in which case p is other than 0),
xe2x80x83with the proviso that:
when the tricyclic group of formula A1 is a 6-methoxytetrahydrobenzo[cd]indole, B cannot represent an NHCOMe group,
the compound of formula (I) cannot represent N-(4-methyl-2,3-dihydro-1H-1-phenalenyl)-1-cyclopropanecarboxamide, N-(4-methyl-2,3-dihydro-1H-1-phenalenyl)-2-chloroacetamide, 2-methyl-1,3,4,5-tetrahydrobenzo[cd]indole-3-carboxamide, N-(5-hydroxy-1,2,2a,3,4,5-hexahydro-4-acenaphthylenyl)acetamide, N-(5-hydroxy-1,2,2a,3,4,5-hexahydro-4-acenaphthylenyl)benzamide or N-(1,2,2a,3,4,5-hexahydro-4-acenaphthylenyl)acetamide,
xe2x80x83it being understood that:
xe2x80x9carylxe2x80x9d is used to denote a phenyl or naphthyl group each optionally substituted by one or more groups, which may be the same or different, selected from hydroxy, linear or branched (C1-C6)-alkoxy, linear or branched (C1-C6)alkyl, cyano, nitro, amino, trihaloalkyl, or halogen atoms,
the expression xe2x80x9coptionally substitutedxe2x80x9d applied to the terms xe2x80x9calkylxe2x80x9d, xe2x80x9calkenylxe2x80x9d and xe2x80x9calkynylxe2x80x9d denotes that those groups may be substituted by one or more groups, which may be the same or different, selected from hydroxy, linear or branched (C1-C6)alkoxy, aryl, or halogen atoms,
the expression xe2x80x9coptionally substitutedxe2x80x9d applied to the terms xe2x80x9ccycloalkylxe2x80x9d and xe2x80x9ccycloalkylalkylxe2x80x9d denotes that the cyclic moiety may be substituted by one or more groups selected from hydroxy, linear or branched (C1-C6)alkoxy, oxo, or halogen atoms,
their enantiomers and diastereoisomers, and addition salts thereof with a pharmaceutically acceptable acid or base.
Amongst the pharmaceutically acceptable acids there may be mentioned by way of non-limiting example hydrochloric acid, hydrobromic acid, sulphuric acid, phosphonic acid, acetic acid, trifluoroacetic acid, lactic acid, pyruvic acid, malonic acid, succinic acid, glutaric acid, fumaric acid, tartaric acid, maleic acid, citric acid, ascorbic acid, methanesulphonic acid, camphoric acid, oxalic acid, etc.
Amongst the pharmaceutically acceptable bases there may be mentioned by way of non-limiting example sodium hydroxide, potassium hydroxide, triethylamine, tert-butylamine, etc.
An advantageous embodiment of the present invention relates to compounds of formula (I) represented by formula (IA): 
wherein:
A forms with the group to which it is bonded a tricyclic system selected from Axe2x80x21, Axe2x80x22, Axe2x80x23 and Axe2x80x24: 
R1 represents a hydrogen atom, a halogen atom or a linear or branched (C1-C6)alkyl, linear or branched (C1-C6)alkoxy, hydroxy or oxo group,
R2 and R3, which may be the same or different, represent a halogen atom or an Ra, ORa, CORa, OCORa or COORa group (wherein Ra represents a hydrogen atom, an optionally substituted linear or branched (C1-C6)alkyl group, linear or branched (C1-C6)trihaloalkyl, an optionally substituted linear or branched (C2-C6)alkenyl group, an optionally substituted linear or branched (C2-C6)alkynyl group, an optionally substituted (C3-C8)cycloalkyl group, an optionally substituted (C3-C8)cycloalkyl-(C1-C6)alkyl group in which the alkyl moiety is linear or branched, or an optionally substituted aryl group),
the symbols (R2)m and (R3)mxe2x80x2 denote that the ring in question may be substituted by from 1 to 3 groups (which may be the same or different) belonging to the definitions for R2 and R3,
X, when A represents a tricyclic system Axe2x80x21, Axe2x80x22, Axe2x80x23 or Axe2x80x24, represents a sulphur atom, a (CH2)q group (wherein q is 1 or 2), a xe2x80x94CHxe2x95x90CHxe2x80x94 group, or an NR4 group (wherein R4 represents a hydrogen atom or an optionally substituted linear or branched (C1-C6)alkyl group),
xe2x80x83or X represents an oxygen atom when A represents the tricyclic system Axe2x80x21,
n is an integer such that 0xe2x89xa6nxe2x89xa63
p is an integer such that 1xe2x89xa6pxe2x89xa63 when n is 1, 2 or 3 and the xe2x80x94(CH2)pxe2x80x94B chain is in the b 20 position and A represents either a group Axe2x80x22, Axe2x80x23 or Axe2x80x24 wherein X represents a xe2x80x94CHxe2x95x90CHxe2x80x94 group, or a group Axe2x80x21,
xe2x80x83and such that 0xe2x89xa6pxe2x89xa63 in all other cases,
it being possible for the (CH2)p chain to be unsubstituted or substituted by one or more groups, which may be the same or different, selected from Ra, ORa, CORa, COORa or halogen atoms,
B represents:
an 
xe2x80x83group wherein Ra is as defined hereinbefore, Z represents an oxygen atom or a sulphur atom, and R5 represents an Ra group or an NR6R7 group wherein R6 and R7, which may be the same or different, represent an Ra group,
or a 
xe2x80x83group wherein Z, R6 and R7 are as defined hereinbefore,
the symbol  denotes that the bond may be single or double provided that the valency of the atoms is respected,
xe2x80x83with the proviso that:
when the tricyclic group of formula Axe2x80x21 is a 6-methoxytetrahydrobenzo[cd]indole, B cannot represent an NHCOMe group,
the compound of formula (I) cannot represent N-(4-methyl-2,3-dihydro-1H-1-phenalenyl)-1-cyclopropanecarboxamide, N-(4-methyl-2,3-dihydro-1H-1-phenalenyl)-2-chloroacetamide, 2-methyl-1,3,4,5-tetrahydrobenzo[cd]indole-3-carboxamide, N-(5-hydroxy-1,2,2a,3,4,5-hexahydro-4-acenaphthylenyl)acetamide, N-(5-hydroxy-1,2,2a,3,4,5-hexahydro-4-acenaphthylenyl)benzamide or N-(1,2,2a,3,4,5-hexahydro-4-acenaphthylenyl)acetamide,
xe2x80x83it being understood that:
xe2x80x9carylxe2x80x9d is used to denote a phenyl or naphthyl group each optionally substituted by one or more groups, which may be the same or different, selected from hydroxy, linear or branched (C1-C6)alkoxy, linear or branched (C1-C6)alkyl, cyano, nitro, amino, trihaloalkyl, or halogen atoms,
the expression xe2x80x9coptionally substitutedxe2x80x9d applied to the terms xe2x80x9calkylxe2x80x9d, xe2x80x9calkenylxe2x80x9d and xe2x80x9calkynylxe2x80x9d denotes that those groups may be substituted by one or more groups, which may be the same or different, selected from hydroxy, linear or branched (C1-C6)alkoxy, aryl, or halogen atoms,
the expression xe2x80x9coptionally substitutedxe2x80x9d applied to the terms xe2x80x9ccycloalkylxe2x80x9d and xe2x80x9ccycloalkylalkylxe2x80x9d denotes that the cyclic moiety may be substituted by one or more groups, which may be the same or different, selected from hydroxy, linear or branched (C1-C6)alkoxy, oxo, or halogen atoms,
their enantiomers and diastereoisomers, and addition salts thereof with a pharmaceutically acceptable acid or base.
A further advantageous embodiment of the present invention relates to compounds of formula (I) represented by formula (IB): 
wherein
A forms with the group to which it is bonded a tricyclic system selected from Axe2x80x31, Axe2x80x32, Axe2x80x33 and Axe2x80x34: 
R1 represents a hydrogen atom, a halogen atom or a linear or branched (C1-C6)alkyl, linear or branched (C1-C6)alkoxy, hydroxy or oxo group,
R2 and R3, which may be the same or different, represent a halogen atom or an Ra, ORa. CORa, OCORa or COORa group (wherein Ra represents a hydrogen atom, an optionally substituted linear or branched (C1-C6)alkyl group, linear or branched (C1-C6)trihaloalkyl, an optionally substituted linear or branched (C2-C6)alkenyl group, an optionally substituted linear or branched (C2-C6)alkynyl group, an optionally substituted (C3-C8)cycloalkyl group, an optionally substituted (C3-C8)cycloalkyl-(C1-C6)alkyl group in which the alkyl moiety is linear or branched, or an optionally substituted aryl group),
the symbols (R2)m and (R3)mxe2x80x2 denote that the ring in question may be substituted by from 1 to 3 groups (which may be the same or different) belonging to the definitions for R2 and R3,
X, when A represents a tricyclic system Axe2x80x31, Axe2x80x32, Axe2x80x33 or Axe2x80x34, represents a sulphur atom, a (CH2)q group (wherein q is 1 or 2), a xe2x80x94CHxe2x95x90CHxe2x80x94 group, or an NR4 group (wherein R4 represents a hydrogen atom or an optionally substituted linear or branched (C1-C6)-alkyl group), or X represents an oxygen atom when A represents the tricyclic system Axe2x80x31,
n is an integer such that 0xe2x89xa6nxe2x89xa63
p is an integer such that 1xe2x89xa6pxe2x89xa63
it being possible for the 
xe2x80x83chain to be unsubstituted or substituted by one or more groups, which may be the same or different, selected from Ra, ORa, CORa, COORa or halogen atoms,
B represents:
an 
xe2x80x83group wherein Ra is as defined hereinbefore, Z represents an oxygen atom or a sulphur atom, and R5 represents an Ra group or an NR6R7 group wherein R6 and R7, which may be the same or different, represent an Ra group,
or a 
xe2x80x83group wherein Z, R6 and R7 are as defined hereinbefore,
the symbol  denotes that the bond may be single or double provided that the valency of the atoms is respected,
xe2x80x83it being understood that:
xe2x80x9carylxe2x80x9d is used to denote a phenyl or naphthyl group each optionally substituted by one or more groups, which may be the same or different, selected from hydroxy, linear or branched (C1-C6)alkoxy, linear or branched (C1-C6)alkyl, cyano, nitro, amino, trihaloalkyl, or halogen atoms,
the expression xe2x80x9coptionally substitutedxe2x80x9d applied to the terms xe2x80x9calkylxe2x80x9d, xe2x80x9calkenylxe2x80x9d and xe2x80x9calkynylxe2x80x9d denotes that those groups may be substituted by one or more groups, which may be the same or different, selected from hydroxy, linear or branched (C1-C6)alkoxy, aryl, or halogen atoms,
the expression xe2x80x9coptionally substitutedxe2x80x9d applied to the terms xe2x80x9ccycloalkylxe2x80x9d and xe2x80x9ccycloalkylalkylxe2x80x9d denotes that the cyclic moiety may be substituted by one or more groups, which may be the same or different, selected from hydroxy, linear or branched (C1-C6)alkoxy, oxo, or halogen atoms,
their enantiomers and diastereoisomers, and addition salts thereof with a pharmaceutically acceptable acid or base.
The preferred compounds of the invention are those wherein A forms with the groups to which it is bonded a tricyclic system of formula A1.
The preferred values for n are 0, 1 and 2.
More especially, the invention relates to compounds wherein A forms with the groups to which it is bonded a tricyclic system of formula Al wherein X represents a (CH2)q group (wherein q is as defined hereinbefore) or a xe2x80x94CHxe2x95x90CHxe2x80x94 group, such as, for example, a 2,3-dihydrophenalene, 1,2-dihydroacenaphthylene or 7,8,9,10-tetrahydrocyclohepta[de]naphthalene tricyclic system.
The preferred values for p are 0, 1 and 2.
The preferred substituents R2 and R3 of the invention are a hydrogen atom and alkoxy and alkyl groups.
The preferred R1 group of the invention is a hydrogen atom.
Advantageously, the invention relates to compounds substituted by the 
chain in the a or c position and more especially to those compounds wherein p represents an integer 0 (in which case the bond  is single), 1 or 2.
The preferred B groups of the invention are the NHCOR5 group wherein R5 is as defined hereinbefore (such as, for example, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, aryl or arylalkyl groups),
and the CONHR6 group wherein R6 is as defined hereinbefore (such as, for example, alkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl, aryl or arylalkyl groups).
More advantageously, the invention relates to the 2,3-dihydrophenalene, 1,2-dihydroacenaphthylene or 7,8,9,10-tetrahydrocyclohepta[de]naphthalene tricyclic systems, each unsubstituted or substituted on the naphthalene moiety by one or more alkoxy or alkyl groups, and substituted in the a or c position by a 
group wherein B represents an NHCOR5 or CONHR6 group (wherein R5 and R6 are as defined hereinbefore).
More especially, the invention relates to the 1,2-dihydroacenaphthylene or 7,8,9,10-tetrahydrocyclohepta[de]naphthalene tricyclic systems,
each unsubstituted or substituted on the naphthalene moiety by one or two alkoxy groups (for example a methoxy group), and substituted in the a or c position by a xe2x95x90CHxe2x80x94B, xe2x95x90CHxe2x80x94CH2xe2x80x94B, xe2x80x94B, xe2x80x94CH2xe2x80x94B or xe2x80x94(CH2)2xe2x80x94B group wherein B represents an NHCOR5 or CONHR6 group wherein R5 and R6 represent an alkyl, alkenyl, alkynyl, trihaloalkyl, cycloalkyl, cycloalkylalkyl, aryl or arylalkyl group, such as, for example, methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, vinyl, propargyl, trifluoromethyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, naphthyl or benzyl.
Very advantageously, the invention relates to 2,3-dihydrophenalene compounds, unsubstituted or substituted on the naphthalene moiety by one or two alkoxy groups (for example a methoxy group),
and substituted in the a or c position by a xe2x95x90CHxe2x80x94B, xe2x95x90CHxe2x80x94CH2xe2x80x94B, xe2x80x94CH2xe2x80x94B or xe2x80x94(CH2)2xe2x80x94B group wherein B represents an NHCOR5 or CONHR6 group wherein R5 and R6 represent an alkyl, alkenyl, alkynyl, trihaloalkyl, cycloalkyl, cycloalkylalkyl, aryl or arylalkyl group, such as, for example, methyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, vinyl, propargyl, trifluoromethyl, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, phenyl, naphthyl or benzyl.
Even more advantageously, the invention relates to N-[(4-methoxy-2,3-dihydro-1H-1-phenalenyl)methyl]acetamide, N-[(4-methoxy-2,3-dihydro-1H-phenalenyl)methyl]propionamide, N-[(4-methoxy-2,3-dihydro-1H-1-phenalenyl)methyl]cyclopropanecarboxamide, N-[(4-methoxy-2,3-dihydro-1H-1-phenalenyl)methyl]butanamide, N-[2-(4-methoxy-2,3-dihydro-1H-1-phenalenyl)ethyl]acetamide, N-[2-(4-methoxy-2,3-dihydro-1H-1-phenalenyl)ethyl]propanamide, N-[2-(4-methoxy-2,3-dihydro-1H-1-phenalenyl)ethyl]-1-cyclopropanecarboxamide, N-(8-methoxy-1,2-dihydro-1-acenaphthylenyl)acetamide, N-[(4-methoxy-2,3-dihydro-1H-1-phenalenyl)methyl]butanamide, N-[2-(9-methoxy-2,3-dihydro-1H-1-phenalenyl)ethyl]acetamide, N-[2-(9-methoxy-2,3-dihydro-1H-1-phenalenyl)ethyl]butanamide, N-[2-(4-methoxy-2,3-dihydro-1H-1-phenalenyl)ethyl]butanamide, N-[2-(4,9-dimethoxy-2,3-dihydro-1H-1-phenalenyl)ethyl]propanamide, N-[2-(4,9-dimethoxy-2,3-dihydro-1H-1-phenalenyl)ethyl]butanamide, N-[2-(4,9-dimethoxy-2,3-dihydro-1H-1-phenalenyl)ethyl]-1-cyclopropanecarboxamide, N-[2-(4,9-dimethoxy-2,3-dihydro-1H-1-phenalenyl)ethyl]acetamide, N-[2-(9-methoxy-2,3-dihydro-1H-1-phenalenyl)methyl]-acetamide, N-[2-(9-methoxy-2,3-dihydro-1H-1-phenalenyl)methyl]butanamide, N-[2-(4,9-dimethoxy-2,3-dihydro-1H-1-phenalenyl)methyl]acetamide, N-[2-(4,9-dimethoxy-2,3-dihydro-1H-1-phenalenyl)methyl]propanamide, N-[2-(4,9-dimethoxy-2,3-dihydro-1H-1-phenalenyl)methyl]butanamide, N-[2-(4,9-dimethoxy-2,3-dihydro-1H-1-phenalenyl)-methyl]-1-cyclopropanecarboxamide, (E)-N-methyl-2-(4-methoxy-2,3-dihydro-1H-1-phenalenylidene)acetamide, (Z)-N-methyl-2-(4-methoxy-2,3-dihydro-1H-1-phenalenylidene)acetamide, N-(1,2-dihydro-1-acenaphthylenylmethyl)acetamide, N-(1,2-dihydro-1-acenaphthylenylmethyl)propanamide, N-(1,2-dihydro-1-acenaphthylenylmethyl)butanamide, N-(1,2-dihydro-1-acenaphthylenylmethyl-1-cyclopropane-carboxamide, N-(8-methoxy-1,2-dihydro-1-acenaphthylmethyl)acetamide, N-(8-methoxy-1,2-dihydro-1-acenaphthylmethyl)propanamide, N-(8-methoxy-1,2-dihydro-1-acenaphthylmethyl)-1-cyclopropanecarboxamide, N-(8-methoxy-1,2-dihydro-1-acenaphthylmethyl)butanamide, N-[2-(1,2-dihydro-1-acenaphthyl)ethyl]acetamide, N-[2-(1,2-dihydro-1-acenaphthyl)ethyl]propanamide, N-[2-(1,2-dihydro-1-acenaphthyl)ethyl]butanamide, N-[2-(1,2-dihydro-1-acenaphthyl)ethyl]cyclopropanecarboxamide, N-[2-(8-methoxy-1,2-dihydro-1-acenaphthyl)ethyl]acetamide, N-[2-(8-methoxy-1,2-dihydro-1-acenaphthyl)ethyl]propanamide, N-[2-(8-methoxy-1,2-dihydro-1-acenaphthyl)ethyl]butanamide, N-[2-(8-methoxy-1,2-dihydro-1-acenaphthyl)ethyl]-1-cyclopropanecarboxamide, N-[2-(1-methoxy-7,8,9,10-tetrahydrocyclohepta[de]naphthalen-7-ylidene)ethyl]propanamide.
The enantiomers and diastereoisomers of the preferred compounds of the invention and addition salts thereof with a pharmaceutically acceptable acid or base form an integral part of the present invention.
The invention relates also to a process for the preparation of the compounds of formula (I) wherein A forms with the groups to which it is bonded a tricyclic system of formula (A1), which process is characterised in that there is used as starting material
a compound of formula (II): 
xe2x80x83wherein R2, R3, R5, X, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
Y2 represents a (CH2)q group (wherein q is 1, 2 or 3, or q is 0 when the symbol  is a single bond),
Y1 represents a (CH2)qxe2x80x2 group (wherein qxe2x80x2 is 0, 1, 2 or 3), substituted by an R1 group as defined hereinbefore,
Y3 represents a (CH2)qxe2x80x3 group (wherein qxe2x80x3 is 0, 1, 2 or 3), substituted by an R1 group as defined hereinbefore, where qxe2x80x2+qxe2x80x3xe2x89xa63 and R1 must represent a hydrogen atom in at least one of the two groups Y1 and Y3,
which is cyclised in a basic medium to yield a compound of formula (III): 
wherein R2, R3, R5, X, Y1, Y2, Y3, m, mxe2x80x2 and the symbol  as defined hereinbefore,
which is then reacted with a Lewis acid to obtain a compound of formula (I/a), which is a particular case of the compounds of formula (I): 
wherein R2, R3, R5, X, Y1, Y2, Y3, m, mxe2x80x2 and the symbol  are as defined hereinbefore, which is then reduced to obtain a compound of formula (I/b), which is a particular case of the compounds of formula (I): 
wherein R2, R3, R5, X, Y1, Y2, Y3, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
or a compound of formula (IV): 
wherein R2, R3, R5, X, Y1, Y2, Y3, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
which is successively
cyclised
reacted with a Lewis acid
to yield a compound of formula (I/c), which is a particular case of the compounds of formula (I): 
wherein R2, R3, R5, X, Y1, Y2, Y3, m, mxe2x80x2 and the symbols  are as defined hereinbefore, which is reduced to obtain a compound of formula (I/d), which is a particular case of the compounds of formula (I): 
wherein R2, R3, R5, X, Y1, Y2, Y3, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
the totality of the compounds (I/a), (I/b), (I/c) and (I/d) constituting the compounds of formula (I/e), a particular case of the compounds of formula (I): 
wherein R1, R2, R3, R5, n, p, X, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
which is either:
subjected to the action of a compound of formula (V): Rxe2x80x2axe2x80x94W (V) wherein Rxe2x80x2a may have any of the meanings of the Ra group as defined hereinbefore with the exception of a hydrogen atom, and W represents a leaving group, such as a halogen atom or a tosyl group, to yield a compound of formula (I/f), which is a particular case of the compounds of formula (I): 
wherein R1, R2, R3, R5, Rxe2x80x2a, n, p, X, m, mxe2x80x2 and the symbol  are as defined hereinbefore, the totality of the compounds of formulae (I/e) and (I/f) constituting the compounds of formula (I/g): 
wherein R1, R2, R3, R5, Ra, n, p, X, m, mxe2x80x2 and the symbol  are as defined hereinbefore, which may be subjected to the action of a thionisation agent, such as Lawesson""s reagent, to obtain a compound of formula (I/h), which is a particular case of the compounds of formula (I): 
wherein R1, R2, R3, R5, Ra, n, p, X, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
or hydrolysed in a basic medium to yield a compound of formula (VI): 
wherein R1, R2, R3, n, p, X, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
which is either:
subjected to the action of a pyrylium salt to yield a compound of formula (VII): 
wherein Hal represents a halogen atom and R1, R2, R3, n, p, X, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
which is condensed with a cyanide salt to obtain a compound of formula (VIII): 
wherein R1, R2, R3, n, p, X m, mxe2x80x2 and the symbols  are as defined hereinbefore,
which is hydrolysed in an acidic or basic medium to yield a compound of formula (IX): 
wherein R1, R2, R3, n, p, X, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
which is subjected, after activation to the acid chloride or in the presence of a coupling agent, to the action of an amine HNR6R7 to yield a compound of formula (I/i), which is a particular case of the compounds of formula (I): 
wherein R1, R2, R3, R6, R7, n, p, X, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
which may be subjected to the action of a thionisation agent, such as Lawesson""s reagent, to obtain a compound (I/j), which is a particular case of the compounds of formula (I): 
wherein R1, R2, R3, R6, R7, n, p, X, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
or subjected to the action of a compound of formula (X):
Zxe2x95x90Cxe2x95x90NR6R7xe2x80x83xe2x80x83(X)
wherein Z, R6 and R7 are as defined hereinbefore, to yield a compound of formula (I/k), which is a particular case of the compounds of formula (I): 
wherein R1, R2, R3, R6, R7, n, p, Z, m, mxe2x80x2 and the symbol  are as defined hereinbefore, which may be condensed with a compound of formula (V) to yield a compound of formula (I/l), which is a particular case of the compounds of formula (I): 
wherein R1, R2, R3, R6, R7, Rxe2x80x2a, n, p, X, Z, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
which compounds (I/a) to (I/l) can be purified according to a conventional separation technique, are converted, if desired, into their addition salts with a pharmaceutically acceptable acid or base, and separated, where appropriate, into their isomers according to a conventional separation technique.
The invention relates also to a process for the preparation of compounds of formula (I) wherein A forms with the groups to which it is bonded a tricyclic system of formula (A2), (A3) or (A4), which process is characterised in that there is used as starting material:
a compound of formula (XI): 
xe2x80x83wherein R2, R5, Y2, m and the symbol  are as defined hereinbefore, and
Yxe2x80x21 represents a (CH2)qxe2x80x2 group substituted by an R1 group wherein qxe2x80x2 and R1 are as defined hereinbefore,
Yxe2x80x23 represents a (CH2)qxe2x80x3 group substituted by an R1 group wherein qxe2x80x3 and R1 are as defined hereinbefore, where 0xe2x89xa6(qxe2x80x2+qxe2x80x3)xe2x89xa64 and R1 must represent a hydrogen atom in at least one of the two groups Yxe2x80x21 and Yxe2x80x23,
and D forms, with the benzene ring, one of the three structures (A2a), (A3a) and (A4a): 
wherein X, R2, R3, m, mxe2x80x2 and the symbol  are as defined hereinbefore,
which is successively
cyclised
reacted with a Lewis acid
to obtain a compound of formula (I/m), which is a particular case of the compounds of formula (I): 
wherein R2, R5, D, Y1, Y2, Yxe2x80x23, m and the symbol  are as defined hereinbefore,
which may be reduced to yield a compound of formula (I/n), which is a particular case of the compounds of formula (I): 
wherein R2, R5, D, Yxe2x80x21, Yxe2x80x22, Yxe2x80x23, m and the symbol  are as defined hereinbefore,
or a compound of formula (XII): 
wherein R2, R5, D, Yxe2x80x21, Y2, Yxe2x80x23, m and the symbol  are as defined hereinbefore,
which is successively
cyclised
reacted with a Lewis acid
to yield a compound of formula (I/o), which is a particular case of the compounds of formula (I): 
wherein R2, R5, D, Yxe2x80x21, Y2, Yxe2x80x23, m and the symbol  are as defined hereinbefore,
which may be reduced to yield a compound of formula (I/p), which is a particular case of the compounds of formula (I): 
wherein R2, R5, D, Yxe2x80x21, Y2, Yxe2x80x23, m and the symbol  are as defined hereinbefore, the totality of the compounds (I/m), (I/n), (I/o) and (I/p) constituting the compounds (I/q), a particular case of the compounds of formula (I): 
wherein R1, R2, R5, D, n, p, m and the symbol  are as defined hereinbefore,
which is either:
subjected to the action of a compound of formula (V) to yield a compound of formula (I/r), which is a particular case of the compounds of formula (I): 
wherein R1, R2, R5, Rxe2x80x2a, D, n, p, m and the symbol  are as defined hereinbefore,
the totality of the compounds (I/q) and (I/r) constituting the compounds (I/s), a particular case of the compounds of formula (I): 
wherein R1, R2, R5, Ra, D, n, p, m and the symbol  are as defined hereinbefore, which may be subjected to the action of a thionisation agent, such as Lawesson""s reagent, to obtain a compound of formula (I/t), which is a particular case of the compounds of formula (I): 
or hydrolysed in a basic medium to yield a compound of formula (XIII): 
wherein R1, R2, D, n, p, m and the symbol  are as defined hereinbefore,
which is either:
subjected successively (as for the synthesis of the compound of formula (I/i) starting from a compound of formula (VI))
to the action of a pyrylium salt
to the action of a cyanide salt
to acidic or basic hydrolysis
to condensation, after activation or in the presence of a coupling agent, with an amine HNR6R7 to yield a compound of formula (I/u), which is a particular case of the compounds of formula (I): 
wherein R1, R2, R6, R7, D, n, p, m and the symbol  are as defined hereinbefore,
which may be subjected to the action of a thionisation agent, such as Lawesson""s reagent, to obtain a compound of formula (I/v), which is a particular case of the compounds of formula (I): 
wherein R1, R2, R6, R7, D, n, p, m and the symbol  are as defined hereinbefore,
or subjected to the action of a compound of formula (X) to yield a compound of formula (I/w), which is a particular case of the compounds of formula (I): 
wherein R1, R2, R6, R7, D, Z, n, p, m and the symbol  are as defined hereinbefore,
which may be condensed with a compound of formula (V) to yield a compound of formula (I/x), which is a particular case of the compounds of formula (I): 
wherein R1, R2, R6, R7, Rxe2x80x2a, D, Z, n, p, m and the symbol  are as defined hereinbefore,
which compounds (I/m) to (I/x) can be purified according to a conventional separation technique, are converted, if desired, into their addition salts with a pharmaceutically acceptable acid or base, and separated, where appropriate, into their isomers according to a conventional separation technique.
Moreover, the compounds of formulae (I/a) to (I/l), which are particular cases of the compounds of formula (I) substituted by the 
chain in the a or c position can be obtained by a preparation process which is characterised in that there is used as starting material a compound of formula (XIV): 
wherein R2, R3, X, m and mxe2x80x2 are as defined hereinbefore and T and Txe2x80x2, which are different, represent a hydrogen atom or a xe2x80x94CHO group,
which is subjected to a Wittig reaction and then to catalytic reduction to obtain a compound of formula (XV): 
wherein R2, R3, X, m and mxe2x80x2 are as defined hereinbefore and Txe2x80x21 and T1 represent a hydrogen atom or a group of formula (XVI): 
wherein G represents a (CH2)nxe2x80x2 group wherein nxe2x80x2=1, 2 or 3 optionally substituted by an R1 group as defined hereinbefore, with the proviso that one of the two groups Txe2x80x21 and T1 represents a hydrogen atom,
which is successively hydrolysed in a basic medium and then decarboxylated by heating to yield a compound of formula (XVII): 
wherein R2, R3, X, m and mxe2x80x2 are as defined hereinbefore and Txe2x80x22 and T2 represent a hydrogen atom or a group of formula (XVIII): 
wherein G is as defined hereinbefore, with the proviso that one of the two groups Txe2x80x22 and T2 represents a hydrogen atom,
which is subjected to cyclisation in the presence of a Lewis acid after activation to the oxalyl chloride, to yield a compound of formula (XIX): 
wherein R2, R3, X, G, m and mxe2x80x2 are as defined hereinbefore, and Txe2x80x23 and T3, which are different, represent a hydrogen atom or an oxo group, which is subjected either:
to a Wittig reaction (optionally followed by reduction) and then to hydrolysis to yield a compound of formula (XX): 
wherein R2, R3, X, G, m, mxe2x80x2 and the symbol  are as defined hereinbefore, and each of T4 and Txe2x80x24 represents a hydrogen atom or forms, with the carbon atom carrying it, 
group wherein p1 is 1, 2 or 3, with the proviso that one of the two groups T4 and Txe2x80x24 represents a hydrogen atom,
or successively
to reduction to the corresponding alcohol
to halogenation in the presence of SOCl2 for example
to condensation with a cyanide salt
to acidic or basic hydrolysis
to yield a compound of formula (XXI): 
wherein R2, R3, X, G, m, mxe2x80x2 and the symbol  are as defined hereinbefore, and Txe2x80x25 and T5, which are different, represent a hydrogen atom or a COOH group,
the totality of the compounds (XX) and (XXI) constituting the compounds of formula (XXII): 
wherein R2, R3, X, G, m, mxe2x80x2 and the symbol  are as defined hereinbefore, and each of Txe2x80x26 and T6 represents a hydrogen atom or forms, with the carbon atom carrying it, 
group wherein p is as defined hereinbefore,
with the proviso that one of the two groups Txe2x80x26 and T6 represents a hydrogen atom,
which compound (XXII) can also be obtained starting from a compound of formula (XIX) by condensation according to a Wittig reaction with a compound containing a nitrile group (followed by optional reduction of the double bond), and hydrolysis of the nitrile, which compound (XXII) is either:
subjected, after activation to the acid chloride or in the presence of a coupling agent, to the action of an amine HNR6R7 to yield a compound of formula (I/y), which is a particular case of the compounds of formula (I): 
wherein R2, R3, X, G, m, mxe2x80x2 and the symbol  are as defined hereinbefore, and each of Txe2x80x27 and T7 represents a hydrogen atom or forms, with the carbon atom carrying it, 
group wherein p, R6 and R7 are as defined hereinbefore,
with the proviso that one of the two groups Txe2x80x27 and T7 represents a hydrogen atom,
which may be subjected to the action of a thionisation agent, such as Lawesson""s reagent, to obtain a compound (I/z), which is a particular case of the compounds of formula (I): 
wherein R2, R3, X, G, m, mxe2x80x2 and the symbol  are as defined hereinbefore, and each of Txe2x80x28 and T8 represents a hydrogen atom or forms, with the carbon atom carrying it, 
group wherein p, R6 and R7 are as defined hereinbefore,
with the proviso that one of the two groups T8 and Txe2x80x28 represents a hydrogen atom,
or activated to the acid chloride, and then treated with an azide, heated to the corresponding isocyanate and then hydrolysed to yield a compound of formula (XXIII): 
wherein R2, R3, X, G, m, mxe2x80x2 and the symbol  are as defined hereinbefore, and each of Txe2x80x29 and T9 represents a hydrogen atom or forms, with the carbon atom carrying it, 
group wherein p is as defined hereinbefore,
with the proviso that one of the two groups T9 and Txe2x80x29 represents a hydrogen atom,
which compound of formula (XXIII) can also be obtained starting from a compound of formula (XIX) by condensation according to a Wittig reaction with a compound containing a nitrile group followed by reduction of the nitrile,
which compound of formula (XXIII) is condensed with:
an acyl chloride ClCOR5 or the corresponding acid anhydride (mixed or symmetrical) wherein R5 is as defined hereinbefore, to yield a compound of formula (I/aa), which is a particular case of the compounds of formula (I): 
wherein R2, R3, X, G, m, mxe2x80x2 and the symbol  are as defined hereinbefore, and each of Txe2x80x210 and T10 represents a hydrogen atom or forms, with the carbon atom carrying it, 
group wherein p and R5 are as defined hereinbefore,
with the proviso that one of the two groups Txe2x80x210 and T10 represents a hydrogen atom,
which may be subjected to the action of a thionisation agent, such as Lawesson""s reagent, and/or substituted after the action of a compound of formula (V) to yield a compound of formula (I/ab), which is a particular case of the compounds of formula (I): 
wherein R2, R3, X, G, m, mxe2x80x2 and the symbol  are as defined hereinbefore, and each of Txe2x80x211 and T11 represents a hydrogen atom or forms, with the carbon atom carrying it, 
group wherein p, Ra, R5 and Z are as defined hereinbefore,
with the proviso that one of the two groups Txe2x80x211 and T11 represents a hydrogen atom,
which compounds (I/y) to (I/ab) can be purified according to a conventional separation technique, are converted, if desired, into their addition salts with a pharmaceutically acceptable acid or base, and separated, where appropriate, into their isomers according to a conventional separation technique.
The compounds (I/m) to (I/v) can also be obtained according to a similar process which is characterised in that there is used as starting material a compound of formula (XXIV): 
wherein R2, D and m are as defined hereinbefore.
The starting materials are:
commercially available,
readily available to the person skilled in the art by using conventional chemical reactions, or
described in the literature, such as, for example, in Application EP 737 670.
The compounds of the invention and the pharmaceutical compositions containing them have proved to be useful in the treatment of disorders of the melatoninergic system. The pharmacological study of the compounds of the invention has in fact shown them to be atoxic, to have very high selective affinity for melatonin receptors and to have significant activities in respect of the central nervous system and, in particular, therapeutic properties in respect of sleep disorders, anxiolytic, antipsychotic and analgesic properties and properties in respect of microcirculation have been found, enabling it to be established that the compounds of the invention are useful in the treatment of stress, sleep disorders, anxiety, seasonal affective disorders, cardiovascular pathologies, insomnia and fatigue due to jetlag, schizophrenia, panic attacks, melancholia, appetite disorders, obesity, insomnia, psychotic disorders, epilepsy, diabetes, Parkinson""s disease, senile dementia, various disorders associated with normal or pathological ageing, migraine, memory loss and Alzheimer""s disease, and in cerebral circulation disorders. In another field of activity, the compounds of the invention appear, in treatment, to have ovulation-inhibiting and immunomodulating properties and they appear to be able to be used in the treatment of cancers.
The compounds will preferably be used in the treatment of seasonal affective disorders, sleep disorders, cardiovascular pathologies, insomnia and fatigue due to jetlag, appetite disorders and obesity. For example, the compounds will be used in the treatment of seasonal affective disorders and sleep disorders.
The present invention relates also to pharmaceutical compositions comprising at least one compound of formula (I) on its own or in combination with one or more pharmaceutically acceptable excipients.
Amongst the pharmaceutical compositions according to the invention there may be mentioned more especially those that are suitable for oral, parenteral, nasal, per- or trans-cutaneous, rectal, perlingual, ocular or respiratory administration and especially tablets or dragees, sublingual tablets, sachets, paquets, gelatin capsules, glossettes, lozenges, suppositories, creams, ointments, dermal gels, and drinkable or injectable ampoules.
The dosage varies according to the sex, age and weight of the patient, the route of administration, the nature of the therapeutic indication, or of any associated treatments and ranges from 0.01 mg to 1 g per 24 hours in 1 or more administrations.